At $100/tach hour, its an affordable path to help get to 1500. (billing is tach)
Is that something unique (ie, selling point) of your club? I've never seen anything other than Hobbes as the billing time (usually with an oil pressure, or for helos, a position sensor). Even with a constant speed prop, the tach is always going to be lower than Hobbes due to ground time and landing at low power.